Tool for dressing grinding wheels



July 8, 1941.

S. J. HARLEY ETAL TOOL FOR DRESSING GRIND ING WHEELS File d March 1, 1940 902mm fan Patented July 8, 1941 U lTED STATES TENT OFFICE Stanley Jafia Harley and John Ernest Wainwright, Coventry, England Application March 1, 1940, Serial No. 321,800 In Great Britain October 1'7, 1939 4 Claims.

This invention relates to tools for dressing grinding wheels and more particularly to diamond and other tools for dressing grinding wheels used for grinding screw threads and other forms.

By those skilled in the art of screw thread grinding the conical form of dressing tool has so far been recognised as one of the most efiicient. Experience has shown, however, that the present pure cone form has certain disadvantages. There is a tendency when overloaded for the tool to break and the fracture does not always occur at the apex or tip of the cone but may take place at or near the base of the cone in which case the tool, which is an expensive item, cannot be re-shaped. In using atool of the pure cone type it is essential if fracture of the tool is to be avoided for the work to be done mainly by the radiused tip of the tool and as little as possible by the taper sides otherwise the accumulation of loose grit between the latter and the wheel will eventually produce such an overload as to fracture the tool. Any attempt to remedy this defect by reducing the contained angle of the tool would result in the tool as a whole being so weakened as to be' unable to withstand the repeated alternating stresses to which it'is subjected when in service.

The object of the present invention is to provide a dressing tool of the kind and for the purposes referred to in which without impairing the efficiency of the tool the risk of fracture is very materially reduced and is in any case localised at or near the tip so that in the event of fracture the tool can be re-shaped and considerable economy in the cost of such tools thereby obtained.

According to this invention the improved tool which is otherwise of conical form is backed-off or formed with a clearance near the radiused tip or apex.

In the accompanying drawing,

Figure 1 is an elevational view of the improved dressing tool, and

Figure 2 is a plan view thereof.

In the form shown in the drawing the improved tool is formed as two integral co-axial cones, a and b. The part a forming the radiused tip or efiective portion of the tool has a contained angle slightly less than that of the part b which constitutes the body of the tool.

The sides of the part a are tangential to the radius at the tip and may extend for any suitable distance before being stepped up or shoulquate clearance between the grinding wheel and the sides of the tool when in service reduces the risk of injury to the tool and confines any fracture that may occur to the vicinity of the junction between the part a and part b so that in the event of the former being broken away the useful life of the tool can be extended by reshaping the part b. A further advantage of the improved tool is that the local clearance which is provided by stepping or backing oil the working end of the tool in the manner above described enables the formation of facets to be discovered which are sometimes overlooked in the case of tools of pure cone form.

We claim:

1. Dressing means for grinding wheels consisting of a diamond formed with a frustro-conical base and an axially aligned conical point integral with said base, said point being of smaller diameter than said base at its juncture therewith in order to leave an annular shoulder on said base facing towards said point to confine fractures within said point, and the solid angle defined by said point being less than the solid angle defined by said base to give clearance between the diamond and the grinding wheel.

2. Dressing means for grinding wheels consisting of a diamond formed with a frustro-conical base and a conical point integral with said base, said point being of smaller diameter than said base at its juncture therewith, and the taper of said point being less than the taper of said base.

3. Dressing means for grinding wheels consisting of a diamond formed with a frustro-conical base and an axially aligned conical point integral with said base, said point being of smaller diameter than said base at its juncture therewith to leave a shoulder on said base facing towards said point.

4. Dressing means for grinding wheels consisting of a jewel formed with a frusto-conical base and a conical point integral with said base, said point being of smaller diameter than said base at its juncture therewith.

STANLEY JAFFA HARLEY. JOHN ERNEST WAINWRIGHT. 

